Syrian warplanes have bombed a rebel headquarters near the Turkish border, missing their target but sending hundreds of Syrians fleeing across the frontier.

Monday’s attack on the Free Syrian Army (FSA) base in Atima, two kilometres from the border, came a day before Turkish and NATO officials were due to start assessing where to station surface-to-air missiles close to the 900km border.

Ahmed, an opposition activist who lives within a few blocks of the base, said: "Two Syrian fighter jets came and fired five rockets. Three have hit farm areas and another two hit buildings near the base."

Ahmed said it was the first time they targeted the FSA base set up by senior rebel Mustafa al-Sheikh when he crossed over to Syria from Turkey two months ago.

The strike was one of the closest to the Turkish border carried out by Syrian jets.

'Increased weapons movement'

Rebels fired anti-aircraft guns at the jets but they were flying too high to be hit, activists said.

Incessant shelling has left Maarat al-Numan in ruins, forcing many of 150,000 residents to flee [Al Jazeera]

"I think the reason for the raid may have something to do with increased weapons movements [from Turkey]," Ahmed said.

Several hundred Syrians fled into Turkey after the raid and were being taken care of by the Turkish army. At least two wounded people were taken across the border.

The Turkish Anatolian news agency said an anti-aircraft shell fired during clashes in another Syrian border town, Harem, hit the roof of a house in the Turkish district of Reyhanli, causing no casualties.

After 20 months of conflict, rebels have been tightening their hold on farmland and urban centres to the east and northeast of Damascus, and have seized a string of military bases in the past 10 days.

On Monday, Syrian rebels have reportedly captured a hydroelectric dam on the Euphrates River in the country's north after days of heavy fighting, activists said.

They have reportedly seized crates of ammunition from the government troops who were protecting the strategic facility in the latest battlefield success for opposition fighters.

Children killed

Activists said rebel fighters overran regime defences and captured the Tishrin Dam, near the town of Manbij, before dawn.

On Sunday, they captured a regime helicopter base outside Damascus before pulling back for fear of government airstrikes.

Amid the intensifying clashes, humanitarian crisis in Syria has been exacerbating, and the death toll continues to rise.

Activists on Sunday reported that a government air raid on a rebel-held village near the capital, Damascus, has killed 10 children as they played outdoors.

The children went out after a lull in fighting in Deir al-Asafir, a village 12km east of Damascus, when fighter jets struck, activists and residents said.

At least 172 people were reportedly killed on Sunday, including 14 children. Most of the deaths were reported in Damascus and its suburbs.

Al Jazeera is unable to independently verify reports of violence, as the Syrian government has placed strict restrictions on reporting.